Range finder



June 4, 1946. s. M. MMNEILLE ETQAL RANGE F'INDER 5 Sheets-She'et 1 Filed June 25, 1943 40 DEV/A rgp j LIGHT FIG. 1.

ZERO ADJUSTER FIG.2B.

.SIERHEN MM NEILLE JOSEPH MIHALYI INVENTORS BYY June 4, 1946. s. M, M cNElLLE ETAL RANGE FINDER 5 Sheets-Sheet? Filed June 25, 1945 LIGHT 31 DEVIATOR STEPHEN M.M NEILLE JOSEPH MIHALYY INVENTORS ZERO ADJUSTER June 4, 1946. s. M. M NEILLE ETAL 2,401,698

RANGE FINDER Filed June 23, 1943 5 Sheets-Sheet I5 STEPHEN M.MACNEILLE JOSEPH MIHALYI INVENTORS W, W

Y ATT'XAZAGT.

June 4, 1946' s. M. M NElLLE ET AL 2,401,698

RANGE FINDER Filed June 25, 1945 5 Sheets-Sheet 4 H 0 a, v 4 g FIG.17.

STEPHEN M.MACNEILLE JOSEPH MIHA LYI IN VENT CRIS BY F I ATTYM T correction setting Patented June 4, 1946 UNITED STATES RANGE rmnnit Stephen MacNeilleand ester, N. Y., assignors to Eastma Kodak .Co

, pany, Rochester,

Jersey Teet mit en Ap lication June 23, 1943,'S erial No. 491,955

, i H p .This invention relates to range finders. This is Case N of a series of applications relating to the same subject and including the following:

Title ig Filed Inventors 5 Mpuntfi for optical ele- 461, 584 Oct. 10,1942 Mihalyi.

men Range finder construc- 461, 585 Oct. 10,1942 Do. 1011., Range finders-Case A. 472, 831 Jan. 19,1943 Do. Range finders Case B 472,832 Jan. 19, 1943 Do. Range finders- Case C. 472, 833 Jan. 19,1943

Do. Range finders-Case D 472, 834 I an. 3 Mihalyi, MacNeille. Range finders case E 472, 835 Jan. Mihalyi, Tuttle. Range finders-Case E. 479,096 Mar. Mihalyia Range finders-Case G. 479, 097 Mar. Range finders-Case H- 479,098 Mar. Rangefinders-Case L 479, 099 Mar. Range finders-Case J 479, 100 Mar. Range finders-:CaseK- 479,101 Mar. Range finders-Case L 479,102 Mar. Range flnders case M. 491, 954 June 23 Range flnders Case N 491, 955 June Range finders-Case O. 491, 956 June 23 Range finders0ase P 526,020 Mar. Range finders-Case T. 508,186 Oct.

Do. Holmes, Mihalyi. Mihalyi, MacNeille. MacNeille, Holmes.

Mihalyi, MacNeille. Mihalyi.

MacNeille. MaeNeille, Mihalyi. MacNeille.

The purpose of the present case is in general similar to that of Case M, namely, to give double sensitivity in the collimating system of an auto- 25 coilimating or range correction setting type of range finder. However, the present case employs an entirely different method.

It is an object of a preferred embodiment of the invention to allow the range correction seti tingelements to be viewed by the. main observer.

In one embodiment the double sensitivity feature is incorporated into prior range correction setting systems such as described in certain of the above listed cases of this series, without altering the main part of the optical system in any way. The invention is also useful with other forms of adjustment coindicant elements as will be pointed out but is far more useful with range systems than with the others. 40

As mentioned in Case M, autocollimating systerns including range correction systems depend for their advantages on the fact that the addition' al optical elements of the collimator system as distinguished from the main range finder optical system, can be made quite small, and hence, more stable in their adjustment. However, when the shift of the adjustment coindicant element image is or the same magnitude as the shift of the main target image due to any maladjustment; the collimator image, 1. e. the image of the adjustment coindicant element, must be read with thesame high order of care as is used in reading the coincidence or stereo depth of the object images. Any system which doubles the sensi- 65,

15 Claims. (01. Sa -2.7)

1 ranetereed na hich is.

dependent omy on the reliability of the main ,.A, ;o d.iue li then rese t inv ntion h creased collimator sensitivity,

to, c si 9f b t "spaced from each other :nient;

2 control gives an ultimate for all practieal purposes are of seminal usually double sensitivity, is obtained by having the collimator beamjrom lone adjustment coindicant element in o e of the pemee i on lane Qt the ran e find permanence-the ran e ind r op cal s m an vf m ne v win oint t e o her a .desflribed ind ta l n mauvet bev d s ds a pa u ar lemmin at, th r wir n e of went l ht b a s a e re e t r means l f j..e rme.rsla i e mee o We art of the element image, which relative movement is at least twice the movement of either part alone. As ap ed to, pure autocollimation, this inventiee teammates a just e t eo ibe .iinnt scale and anindex are aitected oppositelythat is, so that the image of the index moves along the image of the scale as the ra n er. is adj te 11 e, del sitivity featurepermits a larger, more easily read e e eheusedt a The most useful embodiment of the present intion is in pure range correction setting as prim rilrfle q bed .Qe I Q iee The epinseareflil w s P a l a dihedral new: wi i r ed e the com a plane near which the element images are formed. When the terms horizontal and vertical are used merely relative to, one another and iii an optical sense as in an of these rangennder eases, the roof edge or the dihedral reflector should be vertically oriented. The exact orientation of the restof the reflector is not critical, but one pre-- ferried embodiment of the invention employs a porrd pri withdts hypotenuse face facing the incident 11g t; r

ge correction setting marl; is but a single one, the resulting pair of images in any of the forms produced by a dihedral reflector are only when the instrument involves some maladjustment and are in coincidence when the instrument is in proper-adjustment. However, th'ecoin'cidence requires, in this case, that the images be .formed exactly at the Even if it perfect roof edge, it to Hence, in highly accurate systems, we prefer to use an adjustment coindicant element consisting ofstwoiverticallines or marks which may be either dark or bright, and which are roof edge of the dihedral reflector. were possible to make a would not be convenient use such arrangel-Iowever, any shift range finder causes one part of the element light tail shown in Fi 8;

. Figs.- and 11 show Fig. 10A being the fleldof horizontally spaced on one of the comparison element. When the range "Fig. 20 shows a slightly different Fig. 14 shows still another alternative for the detail shown in Fig. 13;

Figs. to 18 illustrate one form of beam splitter for producing a pair of lines to be used as an adjustment coindicant element;

Fig. l9 illustrates a pair of prisms equivalent to the-mirror system of Figs; 15 to 18 r I embodiment of this beam splitter, which is also useful as the receiving dihedral reflector system;

Fig. 21 shows an arrangement alternative to that of Fig.

p. Figs. 22 and 22A illustrate a simplified form of images are equally spaced from the roof edge of the dihedral reflector, and hence will appear in coincidence either when the two beams are reflected toward each other, or if one of these re'- fleeting surfaces is semi-transparent or intercepts only part of the element beam and an additional reflector is included, when the two beams are reflected sideways in the same direction. due to maladjustment of the beam to move toward the roof edge and the other to move away from it so that the image's move apart with twice the rapidity of the'motion of eitherof them.

In one particularly preferred embodiment of the invention an additional reflector is included for directing these two beams toward the eye or the main observer. Also, an additional lens or i an additional optical path of glass is preferably included to. insure that the element images appear to the observer to be in the same plane as the target images so eyepiece of the instrument will serve for both observations. The dihedral reflector and the additional reflector may be formed of two very small prisms which can be mounted in the focal plane of the eyepiece of a range finder, out interfering in any way with the main optical system.

' The advantages of the invention will be fully understood from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 shows a stereo range finder incorporating a simple form of the invention, Fig. 1A being the binocular field of view through the instrument;

Figs. 2, 2A and 2B illustrate in magnified form one detail of Fig. 1;

Fig, 3 shows a similar form of the invention intended forpure autocollimation, Fig. 3A being an enlarged view of one detail of Fig. 3 and Fig. 3B showing the field of view of the scale readin observer;

Fig. 4 shows a preferred embodiment of the invention applied to coincidence range finders, Fig. 4A being the field of view of the observer;

Figs. 5 and 5A show an enlarged detail of Fig. 4'.

Fig, 6 shows an alternative form of the detail shown in Fig. 5;

Figs. '7 and 7A show still another alternative for this detail; v Fig. 8 shows another detail of Fig. 4 greatly enlarged and in perspective;

Fig. 9 shows a preferred alternative ofthe dealternative arrangements for a portion of the instrument shown in Fig; 1, view of the auxiliary observer; 1

7 Figs. 12 and 13 show portions of a range finder i alternative to those shown in Fig. 4;

that a single adjustment of the usually withdihedral reflector according to the invention;

Figs. 23 and 23A illustrate the operation of such a dihedral reflector when a single line adjustment coindicant element is used;

Fig. 24 illustrates why the invention is not sen- "sitive'to rotation of the dihedral reflector. V

a distant In Figs. 1, 1A, 2, 2A and 23 light from object represented by two small aeroplanes is i received at the viewing points of a stereo range finder by optical squares 3i and directed through objectives 32 into focus in comparison planes on the surface of field lenses 33 and 34. The object are viewed stereoscopically by reflectors 35, relay lenses 36, rhombs 31 and eyepieces 38.

The apparent object distance is adjusted by a light deviator 40 operating on one of the object beams. According to the invention, light from a lamp 43, as reflected by prism 44 illuminates an adjustment coindicant element consisting of two horizontally spaced vertical marks 45. In this particular embodiment, the vertical marks are complementary, one continuing where the other leaves ofi as shown in Fig. 1A. L ght from this pair of-lines is collimated by the right hand objective 32 and is directed from one viewing point to the other by a small penta prism 46, and thence by'another penta prism 41, back into-the range finder system to be brought to focus near the other comparison plane 33. At this other comparison plane, a porro prism 48 is positioned parent distance of 75.

and the other 50 semi-transparent and with its roof edge vertically oriented and in the comparison plane. Behind the semi-transparent roof surface is a plane reflector 5|. .The two parts of the element light beamare received respectively on the surfaces 49 and 50. One of. these is transmitted through the surface 50 and after reflection at the reflector 5i back throughthe surface 5i! and the other is reflected first by. the surface 49 and then by the surface 50 so that both of them are directed back toward a semi-transparent reflector 52 so that the images may be viewed through an eyepiece 53 by the eye 54 of an auxiliary observer. When the instrument is slightly out'of adjustment as indicated'by the position of the element'rays in Fig. 2A, this auxiliary observer 54 sees a field of view as shown in Fig. 2B in'which the element images 45' are not in coincidence. By means of a zero adjustor-"55, the maladjustment of the instrument is corrected so that the two element images as they strike the surfaces 49 and 50 are equi-distant from the roof edge of the porro prism 48, at which time the line images 45 will be in coincidence and'appear as a single line. The auxiliary observer 54 by operating the zero adjustor 55 'maintains proper calibration of the instrumentat all times and the main observer is left to judge the apthe object images 307 andto vary this apparent distance bythe lightdeviator usual manner.

Fig. 1 by the use of an adjustment coindicant element which consists-of a scale 92 and an index 63. A large prism BI is used to illuminate this element. Light from the element passes through the same system as before so that the observer sees a scale image 62' and an index image 63' which gives the range directly; In this case, a light deviator 60 is included in one of the object beams and in the element beam rather than separate therefrom, so that autocollimation is secured. The double sensitivity feature produced by the opposed reflectors consisting of the roof surfaces of the prism 48, in this case merely permits a larger scale to be used.

In Fig. 4 a coincidence type range finder is shown in which light from the object being ranged is received on optical squares 65 and directed through objectives 65 to crossed reflectors it? ands?! and thence into focus in superposition in animage field 69, which consists of coplanar comparison planes. The object images are viewed through an eyepiece m by the eye H of an observer. According to the invention as shown in Figs. 4 and 8, light from a lamp l2 reflected by a prism l3 illuminates a single vertical mark 13 which may be either bright or dark. This mark is optically split into two parts by a rhomb 14 so that the light 19 from one part thereof is horiz'ontal-ly displaced from the other. This light is reflected by the prism 58, collimated by the objective 66 and reflected from one viewing point 'to the other and back into th optical system by two smallgprisms 15 and 16 which differ from pure optical squares just sufficiently to compensate for the fact that mark and prism system E3, is, '58 is not in the center of the field B9. The separation of the two parts of the mark causes the light beams therefrom to cross symmetrically between the viewing points. These light beams after reflection by the prism 67 are received on opposite roof surfaces 82 and 83 of a porro prism 11 positioned with its roof edge vertical in the comparison plane 69 at the point conjugate to one midway between the two lines formed by the beam splitter 14. When the instrument is out of adjustment the two beams strike the surfaces 82 and 33 at different distances from the roof edge of the prism 11. One of these beams is reflected by the surface 82 through the other surface which is semi-transparent and thence to the reflecting surface 85 on a prism cemented to the main dihedral reflector, and in turn through the comparison plane 69 to the eyepiece Hi. The other element beam passes through the surface 83 and is reflected by a reflector 3 1, in the comparison plane in this embodiment, back to the surface 83 and thence to the reflector 85 and in turn to the eyepiece Ill. When the instrument is out of adjustment the two images 78' as shown in Figs. 4A and 5A are out of coincidence. These may be brought into coincidence by adjustment of a light deviator 8| As long as the instrument is in adjustment as indicated by coincidence of the images 18', the range may be read directly by adjusting a light deviator 3!] which operates on only one of the object beams and not on the element beam, the calibration being correct when the images 18' are in coincidence.

The arrangement shown in Fig. 8 has the disadvantage that the light paths for the two parts of the adjustment coindicantelement'are slightly coindicant element are coming to focus approximately in the comparison plane 69, or after reflection halfway between the surfaces 82 and 83.

Since the eyepiece 70 is focused on the plane 69,,the additional path between this surface, as reflected by the surface 85, causes the images to appear slightly blurred. In Fig. 6 this is overcome first by moving the whole prism assembly back of the eyepiece focal plane 9! so that the object images are exactly between the surfaces 82 and 83 as shown by the point 533, and second by the addition of a negative lens 94 to compensate for the difference in distance of the comparison plane 94 and the image 93. Actually this lens 94 is very small in diameter compared to the eyepiece 78 since it has to cover only a small part of the field. In fact this Fig. 6 shows that the roofedge of the dihedral reflector is usually not exactly in the focal plane.

However, this arrangement shown in Fig. 6 is not as convenient as that shown fora similar purpose in Fig. '7. In Fig. 7 the prism ll is replaced by a thick one 95, whose front face 96 is optically, after reflection at the various surfaces, at a distance from the plane 5! equal to the actual distance of this surface 56 from the comparison plane 9|. That is, in the absence of any prism assembly the element images, as shown by the broken lines 92, would be formed in the comparison plane 9|. However, due to the thick ness of the glass and the reflection at the Various surfaces, these images are formed at the points 97 which are also in the comparison. plane 9| and hence in focus through the eyepieces of the instrument. Figs. 7 and 7A also show another preferred feature of the invention in which the total reflecting surface 58 covers only a horizontal strip, the rest of the area being preferably painted black. With this arrangement the two parts of the element images 99 and Hill are perfectly complementary to one another even though both of the original parts of the element are continuous. The arrangement shown in Fig. 4 has the disadvantage that the instrument has to be in perfect vertical adjustment in order for the complementary features of the element to carry around to and appear in the element images 18'. In Figs. 7 and 7A, however, the complementary feature is not introduced until at the images themselves and therefore is not so sensitive to adjustment of the instrument.

In Figs. 10, 10A and 11 only part of a range finder system is shown since the remainder of it may be identical to that shown in Fig. 1. Light from a lamp I illuminates a vertical slit I96, the term vertical being used purely in the optical sense. 'A relay lens Iii! forms an image III of this slit on an interface of a prism assembly, one-half m9 of which interface is fully reflecting. The light-passes through a semi-transparent surface IE3 of this prism and the upper half passes over the reflector Hi9 and is reflected IIBof a norm prism. The lower half II1 of the interface receiving the image I I I, is silvered and The operation is of course the'same as for Figure 1.

In Figs. 12 and 13 a coincidence range finder, or at least part thereof since the remainder is identical toFig. 4, is shown in which light from a lamp I25 illuminates a slit I26 which is imaged by'a lens I21 in the central plane of a prism system I28 as a bright line of light I40. The lower half I34 of this interface is silvered to reflect the light back to a semi-transparent interface I32 between two prisms I3I and I33 forming part of the prism assembly I28. The upper half of the interface transmits the light to another semi-transparent surface I36 between prisms I35 and I31 also constituting part of the prism assembly. These two beams then reflected by the surfaces I32 and I36 pass forward and are reflected by the prism 68 around the range finder optical system, from oneviewing point to the other and back to prism 61 and thence into focus toward the comparison plane 65. The same prism assembly I28 now acts to receive both of these beams and to reflect them toward one another forming images I40 in the interface, the part of the image I40 reflected from the surface I32 passes over the reflecting surface I34 whereas the other part as reflected by the surface I36 strikes the mirror I34 and both of them pass to the eyepiece I29 and thence to the eye I of an auxiliary observer.

Fig. 14 shows a slightly different arrangement permitting the auxiliary observer to be on the same side of the comparison plane 69 as the range correction setting mark I26. In this case the central prism interface is made of four parts, the center two, I4I, of which are reflecting so that the images I are directed to the eyepiece I42 and thence to the eye I43 of the auxiliary ob server.

Figs. 15 to 18 show an alternative arrangement for providing the two vertical lines or marks. A lamp I illuminates a transverse slit I5I positioned optically above the comparison field. This slit I5I is imaged by a lens I52 and a dihedral reflector I53 with its roof surfaces preferably silvered and its roof edge parallel to the optic axis of the system, reflects this image outward to two other reflectors I54 constituting another dihedral reflector with its roof edge vertical in the comparison plane. This provides two horizontally spaced vertical lines (actually virtual images of a line) in the comparison plane, without the use of any semi-transparent reflector. V

Fig. 19 shows a prism assembly in which reflecting surfaces I63 and I64 correspond to the dihedral reflectors I53 and I54 respectively.

In the arrangement shown in Fig. 20 a similar pair of dihedral reflectors is used so that light from a lamp I55 illuminates a slit I which is imaged by a pair of lenses IISI and I62 on the dihedral reflector I53. The optical system includes a semi-transparent mirror I63 so that the same pair of dihedral reflectors can be used to receive the returning beams and to direct them upwards through the semi-transparent reflectors I63 and a lens I64 to the eye I65 of an auxiliary observer.

7 In Fig 2l th e semi-transparentreflector I63 is eliminated by having the mark producing optical system on one side of the comparison plane 69 and by having a viewing system symmetrically located atthe other side and consisting of a dihedral reflector I68 to recevie the beams from the reflectors I54 and to direct them through an eyepiece I69 to the eye I10 of an auxiliary observer.

Figs. 22 and 22A illustrate a form of the invention in which an incoming pair of rays I16 from the two parts of the range correcting setting mark strike the two roof surfaces I19 and i535 of a dihedral .reflector having its roof edge in the comparison plane I15. The surface I80 is below one ray so that it passes. straight through and is reflected by a mirror I11 in the comparison plane I15. Both rays after reflectionare again reflected by a semi-transparent mirror I18 to an eyepiece IIII. 7 As long as the instrument is 'out of adjustment the rays I16 strike the roof surfaces I19 and I80 at different distances from the roof edge as shown, but if the instrument is adjusted properly these rays are at the same distance from the roof edge (which is conjugate to a line midway between the two vertical lines constituting themark) and both rays striking the eyepiece IBI are in coincidence.

In Figs. 23 and 23A exactly the same set-up is used with a single beam I85 (with upper and lower halves) arriving to strike the surface I80 part of it to pass over it and the other part to be reflected to the surface I19. As long as the instrument is out of adjustment the eye sees two images as shown and when the instrument is in adjustment the ray I851 strikes the roof edge at the line of intersection I19 and I80 and hence only a single image is then seen. Thus, the invention is broadly operable with but a single mark sending light around the system, but such an arrangement has a very definite disadvantage in practice because at exactly correct setting, the setting system utilizes the roof edge of a dihedral reflector and hence this edge is more critical than is convenient to manufacture. The arrangement shown in Figs. 23 and 23A is only one of many arrangements using a single line but the trouble at the roof edge occurs with all of them. a

Fig. 24 is included to show the advantage of having a dihedral reflector with its roof edge in the comparison plane. If the reflector surfaces I19 and I89 are tipped so as to rotate it is not limited to these specific structures but 7 is of the scope of the appended claims.

What We claim and desire to secure by Letters Patent of the United States is:

1. A range finder of the type having two horizontally spaced viewing points at which light beams are received from the object being ranged, an optical system for directing and focusing the light beams to form images in comparison planes, means for viewing the images and light deviating means for adjusting one of the object images relative to the other, said range finder being characterized by an adjustment coindicant element at least optically in one of the comparison planes, means for projecting through at least the optical equivalent of said optical system, light from said element into focus forming two images, each an image of part of said element, near the other plane, opposed reflector means approximately at said other plane for converting horizontal movement of both images into a relative movement thereof twice that of either image alone.

2. A range finder according to claim 1 in which the adjustment coindicant element consists of both a scale and an index for the scale, the image of the index moving along the image of the scale as the light deviating means is adjusted.

3. A range finder according to claim 1 in which the adjustment coindicant element consists of two vertical lines corresponding to the two images, said lines being at least optically horizontally spaced in said one of the comparison planes.

4. A range finder according to claim 1 in which the adjustment coindicant element consists of two vertical lines corresponding to the two images, said lines being at least optically horizontally spaced in said one of the comparison planes, and the opposed reflector means includes a dihedral reflector with its roof edge vertical and in said other plane.

5. A range finder according to claim 1 in which the opposed reflector means includes a dihedral reflector with its roof edge vertical and in said other plane.

6. A range finder according to claim 1 in which the opposed reflector means includes a porro prism with its roof edge vertical and in said'other plane at the point which is conjugate to the optical middle of the element when the range finder is in proper adjustment.

7. A range finder of the type having two horizontally spaced viewing points at whichlight beams are received from the object being ranged, an optical system for directing and focusing the light beams to form images in comparison planes, means for viewing the images and light deviating means for adjusting one of the object images relative to the other, said range finder being characterized by an adjustment coindicant element consisting of two vertical lines, at least optically horizontally spaced in one of the comparison planes, means for projecting through at least the optical equivalent of said optical system, light from both lines into focus forming two line images near the other plane, a dihedral reflector with its roof edge approximately in the other plane at the point which is conjugate to one optically halfway between the two lines when the range finder is in proper adjustment and means for viewing the two line images.

8. A range finder according to claim 7 in which said element includes a single illuminated ver- 10 tical mark and a beam splitter in front of the mark forming at least one of said lines as a virtual image of said mark.

9. A range finder according to claim 7 in which said lines are virtual images of a mark formed by a beam splitter near said one of the planes.

10. A range finder according to claim 7 in which the dihedral reflector is a porro prism and the latter viewing means includes at least one additional reflector.

11. A range finder according to claim 7 in which the dihedral reflector is right angled and receives light from the images respectively on its two roof surfaces. 7

12. A range finder according to claim 7 in which the dihedral reflector is right angled and at least one additional reflector is included between the dihedral roof surfaces for reflecting the light from the lines sideways and into alignment.

13. A range finder according to claim '7 in which the dihedral reflector is right angled with one roof surface semi-transparent and in which in said other plane behind at least part of said semi-transparent surface there is a plane reflector for reflecting light transmitted by said surface back to the semi-transparent surface which also receives light fromthe other roof surface and directs these two beams of light into .alignment.

14. A range finder according to claim 7 in which the dihedral reflector includes a thick porro prism with another right angled prism cemented to one roof surface of the porro, the interface being semi-reflecting, at least part of the hypotenuse face of the other right angled prism behind the interface being reflecting and the line image viewing means including the other roof ill face of said' other prism for directing to the object image viewing means, light beams transmitted and reflected from the interface.

15. A ranger finder according to claim 7 in which the dihedral reflector includes a thick porro prism with another right angled prism cemented to one roof surface of the porro, the interface, being semi-reflecting, at least part of the hypotenuse face of the other right angled prism behind the interface being reflecting and the line image viewing means including the other roof face of said other prism for directing to the object image viewing means, light beams transmitted and reflected from the interface, the thickness of the porro prism from entrance face to roof edge plus the length of the hypotenuse face of said other prism, all divided by the index of refraction of the prisms being approximately equal to said porro prism thickness whereby said line images will be approximately on said hypotenuse face and in focus in the object image viewing means.

. STEPHEN M. MACNEILLE.

JOSEPH MII-IALYI. 

